Tank Level Altitude Control & Water Hammer Prevention with a Speed-Controlled Butterfly Valve

Altitude Valve Automation at Potable Water Districts

Valve Automation serves a vital role in Potable Water Telemetry Control System Integration. Valves are used in a variety of applications, which broadly include OPEN/CLOSE applications for ON/OFF flow control, as well as MODULATING applications for variable pressure and flow control. This article will address an interesting ALTITUDE CONTROL problem that we recently solved through Valve Automation.

Jim Mimlitz, NRI

One of our newest clients has a distribution infrastructure that is centered around an Elevated Tank that is fed by a remote Booster Pump Station approximately 5 miles away. In addition to the active pump flows, gravity-based flows provide a strong bias toward keeping the level in the Elevated Tank topped off. This gravity-flow bias has caused the tank to overflow on occasion; and it also inhibits fresh water turnover.

In order to solve both problems, the client commissioned NRI to provide a motorized butterfly valve and integration into the system’s Telemetry Controls. The selected butterfly valve was a 6″ Pratt HP 250II. Once in-hand, the butterfly valve was mated to a Quarter-Turn Electric Valve Actuator (Limitorque Model QX-2, Single-Phase, 120VAC, Two-Speed Timer Option) by our Valve Automation Partner Mead O’Brien (St. Louis, MO). Then, the complete Valve/Actuator assembly was field-installed by the customer; and telemetry integration was completed by Navionics Research.

The Limitorque QX is an electric-powered, quarter-turn valve actuator. The QX features microprocessor-based controls and is Limitorque’s successor to the popular LY actuator.

An optional QX feature, which we recommend for non-modulating, altitude valve applications is a TWO-SPEED TIMER. The TWO-SPEED TIMER provides a mechanism for pronounced slowdown of the opening and/or closing operations of the valve, which effectively eliminates water hammer and thus reduces the likelihood of water main breaks. Under normal settings, the QX Actuator time-to-close and time-to-open is approximately 30 seconds. On this project, the TWO-SPEED TIMER was programmed to hold the actuator motor OFF for 18 seconds for every 1 second of motor ON time, which results in a time-to-close and time-to-open of approximately 7 minutes. For optimal efficiency, the timer was activated only within the linear flow versus position range (0%-50% open).

The following video illustrates the the valve actuating from fully-open to fully closed:

24-Hour History Trends After Valve Automation:

Below: Valve Open…

Below: Valve Closed…

Below: Elevated Tank Level. Note 8 Ft. Draw-Down Achieved…

The project was a total success. Free-flow was inhibited during pump OFF cycles, allowing the water level in the elevated tank to draw down lower and refresh, which assists the Water District in maintaining target chlorine residuals and preventing overflows of the Elevated Tank.

The QX Integral Two-Speed Timer was successfully employed to achieve 7 minute time-to-open and 7 minute time-to-close, which tapered the flow starts and stops — thereby eliminating the possibility of water hammers.

Special thanks go out to our partners for their expertise and excellent support. At La Plata Missouri Water Department — Mike Binder; at Henry Pratt Company — Application Engineering Manager Patrick Anderson; at HD Supply Waterworks — James Casteel; and at Mead O’Brien Vicki Hobson.

Two-Speed Timer Retrofit Available

Does your Water Utility already have a Limitorque QX Actuator? If so, please note that the QX Two-Speed Timer is available as a programmable software retrofit, and therefore can be added to legacy installations.

Valve Automation Can Solve Many Potable Water Production and Distribution Problems

Would our state-of-the-art Valve Control Technology help solve a control challenge in your Water District? Give us a call or send us an email. Our Telemetry/Control Systems are designed to leverage this exciting technology; and we’ll be glad to discuss this with you in further detail.

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